The widespread use of Ethernet (registered trademark) networks has created a need for improving the reliability of Ethernet networks and standards for maintenance and management of Ethernet networks are being established. The maintenance and management of an Ethernet network are performed by transmitting Ethernet OAM (Ethernet Operations, Administration, and Maintenance) packets from a computer or the like on a network to which a router belongs to the router.
FIG. 13 illustrates an exemplary configuration of a router that receives Ethernet OAM packets. Functions and other specifics of components included in the router will be described later in detail. When the router receives a packet 1 including a VLAN (Virtual Local Area Network) identifier 2, an input unit 20 processes the packets 1. When the packet 1 is sent to an OAM determining unit 23 through a VLAN extracting unit 21 and a user setting table 22, the OAM determining unit 23 determines whether the packet 1 is an OAM packet or not. If the packet 1 is a packet used for user data communication, an amount of packets permitted by a policer 24 are sent to a buffer 25 and are transmitted to the destination of the packets 1 through a switch 11 and output units 12. When the amount of packets 1 sent to the policer 24 exceeds the amount permitted by the policer 24, the excessive packets 1 are discarded. On the other hand, if the packet 1 is an OAM packet, the packet 1 is sent from the OAM determining unit 23 to an OAM buffer 26, then to a CPU 27, where the packet 1 is processed. All packets 1 determined to be OAM packets by the OAM determining unit 23 are sent to the OAM buffer 26 and the CPU 27.
A related art using OAM packets is disclosed in Japanese Patent Application Laid-Open No. 2004-134969, which is a central office terminal that determines that the central office terminal has received a power-off notification from a customer premises terminal if the central office terminal has detected that OAM packets from the customer premises terminal has been continuously received.